The present invention relates to machine tool spindles, and specifically to the sealing arrangement at the tool-holding end of a machine tool spindle.
Conventionally, a machine tool using rotating cutting tools supported by a machine tool spindle scatters cutting fluid, sometimes including debris and removed material, at the time of processing a workpiece. The scattered cutting fluid, sometimes including debris and removed material, can intrude into the spindle support bearings. The life of the bearings can become significantly shortened, especially in the case of rolling-contact bearings. The cutting fluid can shorten the life of a bearing by deteriorating the lubricant used therein, or by the influence of debris borne by the cutting fluid.
In order to delay the entry of cutting fluid into the bearings, the spindle and support are usually arranged with a seal therebetween. However, for high-speed spindles, the seals must be non-contact seals, for example using a complex path at the tool bearing end, such as one or more labyrinth seals.
FIG. 1 shows a sectional view of a conventional machine tool spindle, while FIG. 2 shows a sectional view of the spindle sleeve and seal area. As illustrated in FIGS. 1 and 2, a conventional tool sleeve 36 is provided at the lower end 18 of the spindle 34, which is rotatably supported on the housing 24 via the bearing 32. A conventional flange 40 is attached to the housing 24 at the lower end thereof, forming a clearance 38 between the bore of the flange 40 and the lower end 18 of the spindle 34. A labyrinth seal 42 is provided inside the flange 40.
The labyrinth seal 42 is capable of delaying the intrusion of cutting fluid into the area of the bearing 32. However, the use of the labyrinth seal 42 does not encourage the discharge of cutting fluid that already intruded into the clearance 38 area.